low blood pressure can be the result of the two damaged valves. Basically, less blood is being pumped around the body than should be. If he is on beta blockers, it is possible he is on too high a dosage. Some people are more sensitive to such drugs than others. If I take more than 1.25mg of beta blockers, my pulse drops to 28.
If there are two damaged valves and if these are the cause of the low pressure, then surgery will be required to repair or replace the valves with mechanical ones. In the angioplasty, did they open the blockages? or leave them? Are they 70% or above? Have they said a bypass is a better option for the blockages?